Multifilaments with time-dependent characteristics, and medical products made from such multifilaments

ABSTRACT

The invention relates to a resorbable multifilament comprising a number of individual resorbable filaments of a first type having a first degradation time and a number of individual resorbable filaments of a second type having a second degradation time, wherein the filaments of the first type and the filaments of the second type are arranged in close relationship to form a composite multifilament having a length and a specific composite cross-section comprising cross-sections of the individual filaments of the first type and second type, wherein the cross-sections of the individual filaments of the first and second type are located at determined relative positions, wherein the relative positions amongst the individual cross-sections of the filaments of the first and second types are invariant over the length of the composite multifilament.

FIELD OF THE INVENTION

The present invention relates to a resorbable polymeric multifilament,and particularly to a resorbable polymeric multifilament withtime-dependent characteristics, and even more particularly to aresorbable polymeric multifilament comprising at least two types offilaments having different degradation times and optionally alsodifferent moduli of elasticity. The invention is also directed tomedical implants and products made from such resorbable polymericmultifilaments.

BACKGROUND OF THE INVENTION

Within the field of surgical repair of soft tissue defects such ashernias, use is often made of a mesh implant fabricated of anon-resorbable material that is inserted to cover the area of the tissuedefect without sewing together the surrounding muscles. Such a meshimplant is most often made from various plastics, which are known to bebiostable and safe for a number of years after implantation. However, itis known that such inert mesh materials can result in discomfort,inflammation, and recurrence of the hernia. Furthermore, permanentlyintroducing a foreign material into the human (or animal) body could beaccompanied with side effects such as migration, chronic inflammation,and chronic pain. The introduction of a relatively large inert implantis also likely to induce a long-term foreign-body-reaction caused by thebody's immune defense system. As a result, the mesh implant may crumpleup and lose its tissue supporting function.

An alternative approach is to make a mesh implant from a biodegradablepolymer. Further, it is known to make a mesh implant from two differentdegradable polymers, either to improve the handling characteristics ofsuch a mesh implant or to match the mechanical characteristics of such amesh implant to the body's healing process of a hernia or other softtissue defect.

For example, U.S. Pat. No. 6,162,962 to Hinsch et al. discloses an arealimplant, which in one embodiment comprises a first resorbable polymerfiber arranged in a basic structure, into which a multifilament threadmade from a second resorbable polymer has been woven for stiffening ofthe areal implant, to thereby facilitate handling during a medicalimplant procedure, e.g. when cutting to size and insertion. Here, thestiffening thread has a degradation time which is shorter than thedegradation time of the polymer fibers of the basic structure.

Another example of degradable mesh implant is presented in U.S. Pat. No.8,016,841, which is assigned to the present assignee and whose entirecontents are incorporated herein by reference for the implant devices,techniques, materials, and methods disclosed therein. This patentdescribes a mesh implant made from at least two different polymericfibers having different degradations times and also different moduli ofelasticity, which are knitted together to form a mesh implant withtime-dependent mechanical behavior. In this mesh implant, a firstpolymer fiber is arranged in a first knit pattern and a second polymerfiber is arranged in a second knit pattern, which is different from thefirst knit pattern and which locks movement of the first knit pattern.U.S. Published Applications 2006/0142786 and 2007/0299542 (now U.S. Pat.No. 8,083,755), which are assigned to the present assignee, alsodescribe various implant devices, techniques, materials, and methods andtheir entire contents are incorporated herein by reference for theimplant devices, techniques, materials, and methods disclosed therein.

SUMMARY OF THE INVENTION

Although the two patents listed above disclose two completely differentways of arranging two types of fibers in relation to each other; i.e. inU.S. Pat. No. 6,162,962 the two fibers are arranged in virtually thesame pattern, whereas in U.S. Pat. No. 8,016,841 the two fibers arearranged in different patterns, the common feature is that themechanical properties of the final products are determined by thespecific knitting or weaving pattern(s) chosen for the particularmanufacturing method. In other words, there are severe constraintsregarding which knitting or weaving patterns can be utilized inpractice. Consequently, there is a need for a more versatile andflexible solution.

Multifilaments as such are also more directly used in the medicalhealthcare industry; e.g. in the form of multifilament sutures, whichare composed of several filaments twisted or braided together. Alsoresorbable polymeric multifilament sutures are known. These sutures aretypically characterized by high initial tensile strength and are mainlyabsorbed by the human body by hydrolysis, during which process thesuture loses tensile strength. The doctor or surgeon must howeverrecognize that loss of tensile strength and the rate of absorption areseparate phenomena, and the doctor or surgeon should further recognizethat accelerated absorption may occur in patients with fever, infection,or protein deficiency, and may lead to an excessively rapid decline intensile strength. To select the proper suture for a specific patient cantherefore be a both delicate and difficult task, and consequently thereis a need for a more robust and versatile suture or multifilamentmaterial.

The above objects are achieved by a resorbable polymeric multifilamentas well as by a resorbable polymeric medical implant as describedherein.

Embodiments of the present invention provide a multifilament whichcomprises at least two types of filaments having different degradationproperties and optionally also different mechanical properties. The twotypes of filaments can be arranged in different geometricalcross-sectional patterns. The first filament type can, for example,occupy about one semicircle of a circular multifilament cross-section,while the second filament type occupies the complementary semicircle. Inanother arrangement, the two filament types can be arranged in aconcentrical pattern, with filaments of the second type surrounding acore made up by filaments of the first type.

If a first filament type is characterized by a relatively shortdegradation time and a high modulus of elasticity, and a second filamenttype is characterized by a relatively long degradation time and lowmodulus of elasticity, it is according to embodiments of the presentinvention possible to compose a multifilament, which, when introducedinto a human or animal body, initially has a high modulus of elasticityand at a later point in time, when the filaments of the first type havedegraded, has a low modulus of elasticity. Multifilaments with suchfeatures can, for example, be used in medical multifilament polymersutures used for soft tissue repair.

According to embodiments of the present invention a multifilamentcomprising at least two types of filaments can be knitted or woven to orinto a medical device such as a medical mesh implant. If such a meshimplant is made from multifilaments comprising filaments of a firsttype, which is characterized by a relatively short degradation time anda high modulus of elasticity, and filaments of a second type, which ischaracterized by a relatively long degradation time and low modulus ofelasticity, the mesh implant will, when implanted in a human or animalbody, initially have a high modulus of elasticity and at a later pointin time, when the filaments of the first type have degraded, have a lowmodulus of elasticity. Mesh implants with such features can, forexample, be used for soft tissue repair. In contrast to existing meshimplants, e.g. mesh implants according to the teachings of theabove-mentioned U.S. Pat. No. 8,016,841, mesh implants made frommultifilaments according to the present invention can be manufactured bythe use of virtually every known knitting or weaving technique whichtoday is used for production of medical mesh implants.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-section of a general multifilament, whichbelongs to the prior art and which is not part of the present invention.

FIG. 2 shows a cross-section of a multifilament according to a firstembodiment of the present invention, comprising two different types offilaments arranged in the shape of two semicircles.

FIG. 3 shows a cross-section of a multifilament according to a secondembodiment of the present invention, comprising three different types offilaments arranged in the shape of three circle sectors.

FIG. 4 shows a cross-section of a multifilament according to a thirdembodiment of the present invention, comprising two different types offilaments disposed in a concentrical arrangement.

FIG. 5 shows a cross-section of a multifilament according to a fourthembodiment of the present invention, comprising three different types offilaments disposed in a concentrical arrangement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a cross-section of a general multifilament 10, whichis not part of the present invention. The multifilament 10 comprises anumber of individual filaments 11. The number of individual filaments 11can principally assume any value, and may range from a few individualfilaments to several hundred individual filaments. The filaments 11 canbe made from natural or synthetic polymers or co-polymers or polymercompositions, and can be non-resorbable or resorbable, but in one singlemultifilament 10 all individual filaments 11 are made from the samepolymer or copolymer or the same polymer composition.

Here, it may be mentioned that multifilaments made from a plurality ofcomponents are known. For example, U.S. patent application Ser. No.11/054,195 to Schemken et al. discloses a method wherein a compositeyarn is formed from a plurality of yarn components, which are spun,cooled, drawn, and textured in parallel relationship, and wherein atleast one of the yarn components is drawn separately. This patentapplication is, however, silent about arranging filaments made fromdifferent kinds of polymers in the same multifilament.

In FIG. 2, a first embodiment of a multifilament 20 according to thepresent invention is schematically illustrated in cross-section. Themultifilament 20 comprises a first type of individual filaments 21 andsecond type of individual filaments 22. In this particular embodiment,the multifilament 20 has a generally circular composite cross-section,whereof the individual filaments 21 of the first type contribute toabout fifty percent (50%) of the total composite cross-sectional areaand whereof the individual filaments 22 of the second type contribute tothe remaining fifty percent (50%) of the total composite cross-sectionalarea. More specifically, the filaments 21 of the first type occupy abouta full semi-circle (at the right-hand side in FIG. 2) of the totalcomposite cross-section, and the filaments 22 of the second type occupythe complementary full semi-circle (at the left-hand side in FIG. 2) ofthe total composite cross-section.

Here it should be mentioned that FIG. 2 illustrates a multifilamenthaving a rather ideal circular cross-sectional shape. In reality, atwo-component multifilament arranged according to the basic principlesshown in FIG. 2 can exhibit a less perfect cross-sectional shape, andcan exhibit a more rectangular shape or square-like shape or a moreirregular shape, the common feature being that filaments of a first typeare arranged in a first geometrical cross-sectional arrangement and thatfilaments of a second type are arranged in a second geometricalcross-sectional arrangement, and that the two cross-sectionalarrangements are arranged in close connection to each other. Inaccordance with the teachings of the first embodiment discussed inconjunction with FIG. 2, each of the two different filament types wouldhowever occupy about one continuous half of the total cross-sectionarea. This type of a two-component multifilament according to thepresent invention can, for example, be manufactured by arranging a firstspool or bobbin with a number of individual filaments of a first typeand arranging a second spool or bobbin with a number of individualfilaments of a second type, and in a parallel relationship bringtogether the two types of filaments into a single multifilamentaccording to the first embodiment of the present invention. During theprocedure, the resulting multifilament can be twisted to improvehandling characteristics and also to ensure that the two types offilaments do not easily split up and separate from each other.

As stated above, in the embodiment shown in FIG. 2, the two differentfilament types each occupies about fifty percent (50%) of the totalcross-section area. It is however within the scope of the presentinvention to let filaments of a first type occupy more than fiftypercent (50%) of the total cross-section area; for example filaments ofa first type can occupy any percentage (for example, any whole number)between 1% to 99% of the total cross-section area, while filaments of asecond type occupy the remaining percentage of the total cross-sectionarea. Also in cases where the two filament types occupy differentpercentages of the total cross-section area, the cross-sectional shapecan be circular or rectangular, or can have any other regular orirregular shape. According to the present invention it is furtherpossible that a multifilament has a total composite cross-section, inwhich individual filaments of a first type and/or a second type occupy anumber of non-continuous portions of the composite cross-section. Forexample, filaments of a first type can form a continuous star-shapedcross-section with a number of star-arms, while cross-sections offilaments of a second type are disposed between the star-arms, therebyoccupying non-continuous portions of the total composite cross-section.

Suitable polymers for the manufacture of filaments of the first type canpreferably be resorbable polymers with a relatively short degradationtime, and non-limiting examples are polymers or copolymers made from themonomer glycolide in pure form, or in combination with paradioxanone,lactide, trimethylene carbonate or caprolactone. Preferably glycolide ispresent in the highest concentration and can be combined with one ormore of the other mentioned monomers in the same material. Yet anothermonomer can be paradioxanone in its pure form, or in combination withlactide, trimethylene carbonate or caprolactone. Suitable polymers forthe manufacture of filaments of the second type can preferably beresorbable polymers with a relatively long degradation time, andnon-limiting examples are polylactide and polyurethanes. Polylactide ispreferably made from the monomer L,L-lactide, which can be combined withsmall amounts of other monomers such as glycolide, trimethylenecarbonate or caprolactone to fine tune elastic and degradationproperties. Examples of degradable polyurethanes are, but not limitedto, polyureaurethanes, polyesterurethanes and polycarbonateurethanes. Ifit is desired to provide a two-component multifilament, which initially,when implanted in a human body, has a high modulus of elasticity andwhich at a later point in time, when the filaments of the first typehave degraded, has a low modulus of elasticity, the polymers of thefirst type of filaments should be characterized by a high modulus ofelasticity while the polymers of the second type of filaments should becharacterized by a low modulus of elasticity. Suitable polymercombinations would, for example, be polyglycolide or blockcopolymerswhere the main monomer component being glycolide in combination with asmall amount of trimethylene carbonate or caprolactone for the firstpolymer type and blockcopolymers with L,L-lactide as the main monomercomponent in combination with trimethylene carbonate or caprolactone.Various polyesterurethanes and polycarbonateurethanes would also be ofparticular use in certain applications, with their long in vivodegradation time and high elasticity, for the second polymer type.

In FIG. 3, a second embodiment of a multifilament 30 according to thepresent invention is schematically illustrated in cross-section. Themultifilament 30 comprises a first type of individual filaments 31, asecond type of individual filaments 32, and a third type of individualfilaments 33. In this particular embodiment, the multifilament 30 has agenerally circular total composite cross-section, wherein the individualfilaments 31 of the first type contribute to about a first third (33%)of the total cross-sectional area, and wherein the individual filaments32 of the second type contribute to about a second third (33%) of thetotal cross-sectional area, and wherein the individual filaments 33 ofthe third type contribute to the remaining third (33%) of the totalcross-sectional area. More specifically, the filaments 31 of the firsttype assume the shape of a circle sector (upper right-hand side in FIG.3) that occupies about a third of the total circular cross-section area,while the filaments 32 of the second type assume the shape of a circlesector (upper left-hand side in FIG. 3) that also occupies about a thirdof the total circular cross-section area, and while the filaments 33 ofthe third type also assume the shape of a circle sector (lower part inFIG. 3) that occupies the remaining and last third of the total circularcross-section area.

Here it should be mentioned that FIG. 3 illustrates a rather idealcircular composite cross-sectional shape. In reality, a three-componentmultifilament arranged according to the basic principles shown in FIG. 3can exhibit a less perfect cross-sectional shape, and can exhibit a morerectangular shape or square-like shape or a more irregular shape. Inaccordance with the teachings of the second embodiment discussed inconjunction with FIG. 3, each of the three different filament typeswould however occupy about one continuous third of the totalcross-section area. This type of a three-component multifilamentaccording to the present invention can, for example, be manufactured byarranging a first spool or bobbin with a number of individual filamentsof a first type and arranging a second spool or bobbin with a number ofindividual filaments of a second type and arranging a third spool orbobbin with a number of individual filaments of a third type, and in aparallel relationship bring together the three types of filaments into asingle multifilament according to the principles discussed inconjunction with the first embodiment of the present invention. Duringthe procedure, the resulting multifilament can be twisted to improvehandling characteristics and also to ensure that the three types ofmultifilaments do not easily split up and separate from each other.

As stated above, in the embodiment shown in FIG. 3, the three differentfilament types each occupies about a third (33%) of the totalcross-section area. It is however within the scope of the presentinvention to let filaments of a first type occupy more or less than athird of the total composite cross-section area, and also filaments ofthe second and third types can occupy more or less than a third of thetotal composite cross-section area. Filaments of any specific type can,for example, occupy any percentage (for example any whole number)between 2% to 98% of the total composite cross-section area. Also incases where the three filament types occupy different percentages of thetotal cross-section area, the cross-sectional shape can be circular orrectangular, or can have any other regular or irregular shape. Accordingto the present invention it is further possible that a multifilament hasa total composite cross-section, in which individual filaments of afirst type and/or a second type and/or a third type occupy a number ofnon-continuous portions of the composite cross-section.

Suitable polymers for the manufacture of filaments of the first type canpreferably be resorbable polymers with a relatively short degradationtime, and non-limiting examples are polymers or copolymers made from themonomer glycolide in pure form or in combination with paradioxanone,lactide, trimethylene carbonate or caprolactone. Preferably glycolide ispresent in the highest concentration and can be combined with one ormore of the other mentioned monomers in the same material. Suitablepolymers for the manufacture of filaments of the second type canpreferably be resorbable polymers with a relatively longer degradationtime, and non-limiting examples are polyparadioxanone andblockcopolymers of glycolide having a relative high content oftrimethylene carbonate in the center segment. Also various copolymers oflactide in combination with trimethylene carbonate and/or caprolactoneto increase elasticity and reduce degradation times are preferable.Suitable polymers for the manufacture of filaments of the third type canpreferably be resorbable polymers with the relatively longestdegradation time, and non-limiting examples are polylactide andpolyurethanes. Polylactide is preferably made from the monomerL,L-lactide which can be combined with small amounts of other monomerssuch as glycolide, trimethylene carbonate or caprolactone to fine tuneelastic and degradation properties. Examples of degradable polyurethanesare, but not limited to, polyureaurethanes, polyesterurethanes andpolycarbonateurethanes. If it is desired to provide a three-componentmultifilament which initially when implanted in a human body has a highmodulus of elasticity and which at a later point in time, when thefilaments of the first type have degraded, has a lower modulus ofelasticity, and at an even later point in time, when also the filamentsof the second type have degraded, has an even lower modulus ofelasticity, the polymers of the first type of filaments should becharacterized by a high modulus of elasticity, while the polymers of thesecond type of filaments should be characterized by a relatively lowermodulus of elasticity, and while the polymers of the third type offilaments should be characterized by the relatively lowest modulus ofelasticity. Suitable polymer combinations would, for example, bepolymers or copolymers made from the monomer glycolide in pure form orin combination with paradioxanone, lactide, trimethylene carbonate orcaprolactone. Preferably glycolide is present in the highestconcentration and can be combined with one or more of the othermentioned monomers in the same material. Suitable polymers for the firstpolymer type are polyparadioxanone and blockcopolymers of glycolidehaving a relative high content of trimethylene carbonate in the centersegment. Also various copolymers of lactide in combination withtrimethylene carbonate and/or caprolactone to increase elasticity andreduce degradation times are preferable. Suitable polymers for thesecond polymer type are polylactide and polyurethanes. Polylactide ispreferably made from the monomer L,L-lactide which can be combined withsmall amounts of other monomers such as glycolide, trimethylenecarbonate or caprolactone to fine tune elastic and degradationproperties. Examples of degradable polyurethanes are, but not limitedto, polyureaurethanes, polyesterurethanes and polycarbonateurethanes forthe third polymer type.

In FIG. 4, a third embodiment of a multifilament 40 according to thepresent invention is schematically illustrated in cross-section. Themultifilament 40 comprises a first type of individual filaments 41 andsecond type of individual filaments 42. In this particular embodiment,the multifilament 40 has a generally circular composite cross-section,wherein the individual filaments 41 of the first type constitute thecore of the composite cross-section and wherein the individual filaments42 of the second type are arranged in a concentrical arrangement withthe individual filaments 42 of the second type disposed in a circularshell around the core of individual filaments 41 of the first type. Forillustrative purposes only, in FIG. 4 there is an empty gap between thecore and the circular shell; in reality this gap can be infinitelysmall, e.g. non-existing.

Here it should be mentioned that FIG. 4 illustrates a multifilamenthaving a rather ideal circular cross-sectional shape. In reality, atwo-component multifilament arranged according to the basic principlesshown in FIG. 4 can exhibit a less perfect shape, and can exhibit a moreirregular shape, the common feature still being that individualfilaments of a second type are arranged around and at least partly coverindividual filaments of a first type. This type of a two-componentmultifilament according to the third embodiment of the present inventioncan, for example, be manufactured by arranging a first spool or bobbinwith a number of individual filaments of a first type and arranging asecond spool or bobbin with a number of individual filaments of a secondtype, and by, for example, providing a nozzle or other device by whichthe filaments of the second type are guided and distributed over a coremade up of the filaments of the first type. By this production method,the individual filaments of both the first and second types can bemanufactured by, for example, melt extrusion at an earlier point intime.

Suitable exemplifying polymers and polymer combinations for themanufacture of a multifilament according to this third embodiment arethe same as discussed above in conjunction with the first embodiment ofthe invention shown in FIG. 2. However, care should be taken (in lightof the specific medical use of the multifilament) when choosing thespecific polymer and filament configuration, i.e. if a first resorbablepolymer having a relatively short degradation time is chosen for themultifilament core and second resorbable polymer having a relativelylong degradation time is chosen for the filament circumference, a hollowmultifilament will be the temporary result when the core has degraded;whereas a thinner multifilament will be the temporary result if apolymer with relatively short degradation time is chosen for thefilament circumference provided around a filament core made from apolymer with a relatively long degradation time.

In FIG. 5, a fourth embodiment of a multifilament 50 according to thepresent invention is schematically illustrated in cross-section. Themultifilament 50 comprises individual filaments 51 of a first type,individual filaments 52 of a second type, and individual filaments 53 ofa third type. In this particular embodiment, the multifilament 50 has agenerally circular composite cross-section, wherein the individualfilaments 51 of the first type constitute the core of the compositecross-section and wherein the individual filaments 52 of the second typeare arranged in a concentrical arrangement with the individual filaments52 of the second type disposed around the core of individual filaments51 of the first type, and wherein the filaments 53 of the third type arearranged in a concentrical arrangement with individual filaments 53 ofthe third type disposed around the individual filaments 52 of the secondtype. Thus, the individual filaments 52 constitute an inner circularshell and the individual filaments 53 constitute an outer circularshell, both shells being concentrically arranged around a common core ofindividual filaments 51. For illustrative purposes only, in FIG. 4 thereare empty gaps between the core and the inner circular shell as well asbetween the inner circular shell and the outer circular shell. Inreality these gaps can be infinitely small, e.g. non-existing.

Suitable exemplifying polymers and polymer combinations for themanufacture of a multifilament according to this fourth embodiment arethe same as discussed above in conjunction with the second embodiment ofthe invention shown in FIG. 3. However, the same considerations applyhere regarding the choice of specific polymer configurations as wasdiscussed in conjunction with the third embodiment shown in FIG. 4, i.e.if a resorbable polymer having the relatively shortest degradation timeis provided as polymer filaments arranged in a core, a hollowmultifilament will be the temporary result when the core has degraded;and if instead a resorbable polymer having the relatively shortestdegradation time is provided as polymer filaments arranged as an innercircular shell, a hollow multifilament, with a core and an outercircular shell and a gap therebetween, will be the temporary result whenthe inner circular shell has degraded.

A common and very important feature for all embodiments of the presentinvention is that the relative cross-sectional positions for theindividual filaments of any type remain the same wherever across-section is taken along the length of a multifilament according tothe present invention. This invariant cross-section feature prevailseven if, for example, a multifilament is twisted during the productionthereof.

It will be understood that the invention is not restricted to the abovedescribed exemplifying embodiments thereof and that many modificationsare possible. In particular, it should be understood that more thanthree different polymer filaments can be arranged in a basicallyparallel relationship, as exemplified by the first and secondembodiments shown in FIG. 2 and FIG. 3, respectively, or in a basicallyconcentric relationship, as exemplified by the third and fourthembodiments shown in FIG. 4 and FIG. 5, respectively. It should also bementioned that herein the terms “resorbable”, “absorbable”, “degradable”and “biodegradable” are used interchangeably, and all refer to filamentsor multifilaments and medical products made thereof which degrade in ahuman or animal body.

Multifilaments according to the present invention can be used directlyin medical sutures, i.e. a single multifilament can be used as a suture,or several multifilaments can be twisted or braided together to form asuture. When implanted in a human or animal body, such a suture willdegrade with time, and will in particular exhibit time-dependentcharacteristics; for example become more elastic when filaments of afirst type having a short degradation time and high modulus ofelasticity have degraded and only filaments of a second type, havinglonger degradation time and a low modulus of elasticity, remain in thehuman or animal body. Such a multifilament can thereby be adapted to thebody's healing process, i.e. initially be relatively inelastic when thedamaged tissue needs full support and gradually lose strength as thetissue heals and becomes stronger. An important feature ofmultifilaments according to the present invention is that an outersurface of the multifilament can be made very smooth and regular. Due tothis smooth and regular outer surface, a multifilament according to thepresent invention can be used in virtually all types of knitting orweaving machines that today are used to, for example, produce medicalimplant devices. This is in contrast to braided, twisted multifilamentsaccording to prior art, which would get stuck in most known knitting orweaving machines.

Resorbable multifilaments according to the present invention can also beused in medical products such as medical mesh implants, wherein severalmultifilaments are woven or knitted together to form a resorbable meshimplant. Such a medical mesh implant will then exhibit time-dependentcharacteristics, e.g. become more elastic when filaments of a firsttype, having short degradation time and a high modulus of elasticity,have degraded and only filaments of a second type, having longerdegradation time and a low modulus of elasticity, remain in the human oranimal body. Such a resorbable mesh can thereby be adapted to the body'shealing process, i.e. initially be relatively inelastic when the damagedtissue needs full support and gradually lose strength as the tissueheals and becomes stronger. Such time-dependent characteristics can beachieved with virtually any known knitting or weaving technique, i.e.the time-dependent characteristics are not dependent on a particularknitting or weaving pattern. This last feature is in contrast to knownmedical mesh implants, wherein specific time-dependent mechanicalcharacteristics can only be achieved by selecting specific knitting orweaving patterns, which may include a first specific knitting or weavingpattern for a first type of fibers, filaments or multifilaments having arelatively short degradation time and another specific knitting orweaving pattern for a second type of fibers, filaments or multifilamentshaving a relatively longer degradation time.

What is claimed is:
 1. A resorbable multifilament, comprising: a numberof individual resorbable filaments of a first type having a firstdegradation time, and a number of individual resorbable filaments of asecond type having a second degradation time; wherein the seconddegradation time is different from the first degradation time; andwherein the filaments of the first type and the filaments of the secondtype are arranged in close relationship to form a compositemultifilament having a length and a specific composite cross-section,which comprises cross-sections of the individual filaments of the firsttype and cross-sections of the individual filaments of the second type;wherein the cross-sections of the individual filaments of the first andsecond types are located at determined relative positions; and whereinthe relative positions amongst the individual cross-sections of thefilaments of the first type and the individual cross-sections of thefilaments of the second type are invariant over the length of thecomposite multifilament.
 2. The resorbable multifilament according toclaim 1, wherein the individual filaments of the first type have a firstmodulus of elasticity and the individual filaments of the second typehave a second modulus of elasticity, and wherein the second modulus ofelasticity is different from the first modulus of elasticity.
 3. Theresorbable multifilament according to claim 1, wherein the filaments ofthe first type occupy a first continuous portion of the compositecross-section.
 4. The resorbable multifilament according to claim 1,wherein the filaments of the first type occupy a number ofnon-continuous portions of the composite cross-section.
 5. Theresorbable multifilament according to claim 1, wherein the multifilamenthas a generally circular cross-section, and wherein the filaments of thefirst type occupy a first circle sector of the circular cross-sectionand the filaments of the second type occupy a second circle sector ofthe circular cross-section.
 6. The resorbable multifilament according toclaim 5, wherein the first circle sector is a semi-circle and the secondcircle sector is a complementary semi-circle.
 7. The resorbablemultifilament according to claim 1, wherein the multifilament has agenerally circular cross-section, and wherein the filaments of the firsttype constitute a core of the circular cross-section and the filamentsof the second type are disposed concentrically around the core.
 8. Theresorbable multifilament according to claim 1, wherein the multifilamenthas a generally circular cross-section, and wherein the filaments of thefirst type constitute a core of the composite cross-section and thefilaments of the second type are disposed concentrically around thecore, and wherein the first degradation time is longer than the seconddegradation time.
 9. The resorbable multifilament according to claim 8,wherein the individual multifilaments of the first type have a firstmodulus of elasticity and the individual multifilaments of the secondtype have a second modulus of elasticity, and wherein the first modulusof elasticity is lower than the second modulus of elasticity.
 10. Theresorbable multifilament according to claim 1, wherein the multifilamenthas a generally circular cross-section, and wherein the filaments of thefirst type constitute a core of the composite cross-section and thefilaments of the second type are disposed concentrically around thecore, and wherein the first degradation time is shorter than the seconddegradation time.
 11. The resorbable multifilament according to claim10, wherein the individual multifilaments of the first type have a firstmodulus of elasticity and the individual multifilaments of the secondtype have a second modulus of elasticity, and wherein the first modulusof elasticity is higher than the second modulus of elasticity.
 12. Aresorbable multifilament, comprising: a number of individual resorbablefilaments of a first type having a first degradation time, and a numberof individual resorbable filaments of a second type having a seconddegradation time, and a number of individual resorbable filaments of athird type having a third degradation time; wherein the seconddegradation time is different from the first degradation time, and thethird degradation time is different from the second degradation time andis also different from the first degradation time; and wherein thefilaments of the first type, the filaments of the second type and thefilaments of the third type are arranged in close relationship to form acomposite multifilament having a length and a specific cross-section,which comprises cross-sections of the individual filaments of the firsttype, cross-sections of the individual filaments of the second type andcross-sections of the individual filaments of the third type; whereinthe cross-sections of the individual filaments of the first, second andthird types are located at determined relative positions; and whereinthe relative positions amongst the individual cross-sections of thefilaments of the first type, the individual cross-sections of thefilaments of the second type and the individual cross-sections of thefilaments of the third type are invariant over the length of thecomposite multifilament.
 13. The resorbable multifilament according toclaim 12, wherein the individual filaments of the first type have afirst modulus of elasticity, the individual filaments of the second typehave a second modulus of elasticity and the individual filaments of thethird type have a third modulus of elasticity, and wherein the secondmodulus of elasticity is different from the first modulus of elasticityand the third modulus of elasticity is different from the second modulusof elasticity and is also different from the first modulus ofelasticity.
 14. The resorbable multifilament according to claim 12,wherein the multifilament has a generally circular cross-section, andwherein the filaments of the first type occupy a first circle sector ofthe circular cross-section, the filaments of the second type occupy asecond circle sector of the circular cross-section and the filaments ofthe third type occupy a third circle sector of the circularcross-section.
 15. The resorbable multifilament according to claim 12,wherein the multifilament has a generally circular cross-section, andwherein the filaments of the first type constitute a core of thecomposite cross-section, the filaments of the second type are disposedconcentrically around the core and the filaments of the third type aredisposed concentrically around the filaments of the second type.
 16. Theresorbable multifilament according to claim 15, wherein the thirddegradation time is shorter than the second degradation time and thesecond degradation time is shorter than the first degradation time. 17.The resorbable multifilament according to claim 16, wherein theindividual filaments of the first type have a first modulus ofelasticity, the individual filaments of the second type have a secondmodulus of elasticity and the individual filaments of the third typehave a third modulus of elasticity, and wherein the first modulus ofelasticity is lower than the second modulus of elasticity and the secondmodulus of elasticity is lower than the third modulus of elasticity. 18.A medical mesh comprising the multifilament according to claim
 1. 19. Amedical mesh comprising the multifilament according to claim 17.